The present invention relates to a spindle device of a machine tool spouting spray coolant from the tip of a tool.
As to machining by machine tools, much coolant is supplied into machining points to cool and lubricate workpieces and tools, or to eliminate cutting chips. In this case, there are many problems, such as ill effects to an environmental pollution and human health due to coolant, high cost resulting from waste oil disposal of the coolant, shortening the life of a tool resulting from undercooling the workpieces, and sliding friction due to excessive coolant at a minute slitting of a tool. Besides, much coolant adheres to the cutting chips in machining, and therefore, when treating and recycling the cutting chips, the adhesive coolant needs separating from the machine tool.
In recent years, to settle the above problems, there appear machine tools performing so-called dry cutting that cut as supplying spray into machining points. Here, the spray is formed from a very small quantity of coolant.
Applicant has already practiced a machine tool for the dry cutting, for example, its spindle device is like FIG. 3.
In this figure, 2 is a spindle, 10 is a canister, 11 is a steel ball, 12 is a clamp-rod, 13 is a transiently clamping ring member, 14 is a receiving spring ring, 15 is a compression spring, 16 is a longitudinal guiding bar member, 17 is a gas-liquid passage, 18 is a coolant atomizing means, 103 is a coolant nozzle hole member, and 22 is a disc spring. The atomizing means 18 comprises an atomizing nozzle 23, a compressed air supplying valve 24, and a compression spring 19. The numeral 31 is a pull-stud of a tool holder.
In thus structure, a central hole of the compressed air supplying valve 24, a front central hole of the longitudinal guiding bar member 16 and an inner hole of the coolant nozzle hole member 103 form an in-spindle spray coolant passage 100. Besides, a central hole of the pull-stud 31 forms an in-holder spray coolant passage 102.
The above spindle device is operated as the following. That is, spray coolant spouts from an outlet of the atomizing nozzle 23 within the spindle 2 into the in-spindle spray coolant passage 100. The spouted spray coolant flows from the coolant nozzle hole member 103 into the canister 10 having a comparative large diameter, and then, flows into the air from the tip of the tool through the in-holder spray coolant passage 102 and a spray coolant passage formed in the center of the tool fixed to the tool holder.
According to this kind of machine tool, even if the tool cuts deep positions of workpieces, a tool machining part is effectively lubricated by the spray coolant spouted from the tip of the tool. Accordingly, cutting is rationally achieved.
However, in the above conventional machine tool, the spray coolant which has reached the inside of the central hole of the longitudinal guiding bar member 16, flows into the air through openings between its parts. Therefore the coolant is wasted.
In addition, because the central hole of the longitudinal guiding bar member 16 has a diameter comparative larger than those of front and rear passages, the reached spray coolant is liquidized. Therefore the liquefaction hinders stable supply of the coolant to the machining position of the workpiece, as well as response to orders to start or stop spouting the spray coolant from the tip of the tool.
An object of the invention is to provide a spindle device of a machine tool that can settle the above problems.
To achieve the above object, the invention is characterized by a spindle device of a machine tool that fixes a pull-stud of a tool holder on the tip of a spindle through clamping means mechanically detachably. As shown therein, an extension passage is formed in the state that an in-spindle spray coolant passage formed in the center of the spindle is extended forward. Besides, the in-spindle spray coolant passage is communicated with an in-holder spray coolant passage formed in the center of the tool holder through the extension passage.
Accordingly, the in-spindle spray coolant passage, the in-holder spray coolant passage and the extension passage are hardly different in their diameters, thereby communicating closely each other. Therefore, spray coolant passing these passages is prevented liquefying due to differences between their diameters, and stably spouts from the tip of the tool of the tool holder. Besides, since these passages communicate with each other closely, the spray coolant is prevented flowing in vain into the air through the openings between the parts of the machine tool. Moreover, since the extension passage is formed to the spindle side, a structure of the conventional tool holder can be used as it is.
This invention can be materialized as follows.
That is, a slipping prevention ring member is mounted on the tip of the central hole of a little to the pull-stud of the longitudinal bar member, and the extension passage member is freely displaced in longitudinal direction of the tool holder through the slipping prevention ring. The extension passage member forms a cylinder, and is pressed forward by a spring, and therefore its tip projects out of the slipping prevention ring. Accordingly, regardless of rotations of the spindle, the coolant passages of the extension passage member and the coolant atomizing means can keep their close connection by spring force.
Besides, a flange is provided to the rear end face of the extension passage member, so as not to slip out from the slipping prevention ring in displacing slidably.
The tip of the extension passage member always projects forward from the slipping prevention ring by spring force.